Expandable tire building drum with alternating fixed and expandable segments, and contours for sidewall inserts

ABSTRACT

An expandable tire building drum, having alternating fixed ( 226, 326, 426 ) and expanding ( 228, 328, 428 ) segments (e.g., 24 of each) in a center section ( 220, 320, 420 ) of the drum. The expanding segments are axially-extending and circumferentially spaced from one another, and are contoured (have recesses, or grooves) to accommodate tire components such as sidewall inserts. Two different mechanisms for expanding the center section are described. A first mechanism includes two wedge elements ( 358 ) which are axially moveable away from one another to expand the center section. Ramp elements ( 348 ) associated with the expanding segments ( 328 ) may thus be moved radially outward. Rubber bands ( 358 ) provide a restoring force for collapsing the center section. A second mechanism includes two guide rings ( 458 ) which are axially moveable towards one another for expanding the center section, and away from one another to collapse the center section. Overlapping links ( 462, 464 ) are provided between the guide rings and a support element ( 448 ) supporting the expanding segments ( 428 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a Divisional application of U.S. application Ser. No.09/960,215 having a filing date of Sep. 21, 2001 and a common assigneewith present application.

[0002] This application relates to U.S. patent application Ser. No.09/960,211 entitled TIRE BUILDING DRUM HAVING EXPANDABLE CENTER SECTIONAND INDEPENDENTLY EXPANDABLE BEAD LOCK ASSEMBLIES IN THE END SECTIONS,filed on Sep. 21, 2001.

TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to tire building drums for layingup tire carcasses, more particularly to drums which are expandablebetween a collapsed position and an expanded position.

BACKGROUND OF THE INVENTION

[0004] It is known that in making vehicle tires, for example forautomobiles, that manufacture of a so-called carcass is first achievedby successively assembling several different components. In other words,the different carcass types included in a production range can bedistinguished from one another depending on the presence thereon of thevarious accessory components and/or the typology of the accessorycomponents themselves.

[0005] By way of example, when carcasses for tubeless tires are to beproduced, that is tires that in use do not require the presence of aninner tube, the main components can be considered to include a so-calledinner liner that is a layer of elastomeric air-impervious material, acarcass ply, a pair of annular metal elements, commonly referred to asbead cores, around which the opposite ends of the carcass ply are foldedas well as a pair of sidewalls made of elastomeric material, extendingover the carcass ply at laterally opposite positions. The accessorycomponents may in turn comprise of one or more additional carcass plies,one or more reinforcing bands for overlying the carcass ply or plies atthe areas turned up around the bead cores (chafer strips), and others.

[0006] It is well known that the components of most pneumatic tireconstructions must be assembled in a way which promotes good tireuniformity in order to provide proper tire performance. For example, atread which “snakes” as it goes around the tire circumference will causewobbling as the tire is operated. For example, a carcass ply which islopsided (longer cords on one side of the tire than the other side) cancause a variety of tire nonuniformity problems including staticimbalance and radial force variations. For example, a tire which is notmeridionally symmetric (e.g., tread not centered between beads) cancause a variety of tire nonuniformity problems including coupleimbalance, lateral force variations, and conicity. Therefore, in orderto meet typical tire performance requirements, the tire industrygenerally expends considerable effort in producing tires with gooduniformity. Tire uniformity is generally considered to mean tiredimensions and mass distributions which are uniform and symmetricradially, laterally, circumferentially, and meridionally, therebyproducing acceptable results for measurements of tire uniformityincluding static and dynamic balance, and also including radial forcevariation, lateral force variation, and tangential force variation asmeasured on tire uniformity machines which run the tire under load on aroad wheel.

[0007] Although certain degrees of tire nonuniformity can be correctedin post-assembly manufacturing (e.g., by grinding), and/or in use (e.g.,applying balance weights to the rim of a tire/wheel assembly), it ispreferable (and generally more efficient) to build-in tire uniformity asmuch as possible. Typical tire building machines comprise a tirebuilding drum around which the tire components are wrapped in successivelayers including, for example, an innerliner, one or more carcass plies,optional sidewall stiffeners and bead area inserts (e.g., apex),sidewalls and bead wire rings (beads). After this layering, the carcassply ends are wrapped around the beads, the tires are blown up into atoroidal shape, and the tread/belt package is applied.

[0008] Commonly-owned U.S. Pat. No. 5,591,288 (hereinafter referred toas “Becker”) discloses mechanical tire building drums for buildingextended mobility pneumatic tires, and more specifically to a tirebuilding drum having contours or depressions in its surface tofacilitate building certain tire designs. Attention is also directed tocorresponding published European Patent Application No. 0 634 266 A2.

[0009] As noted by Becker, tire performance can be affected by addingcomponents to the tire or by adjusting the location of tire componentsin the tire during the tire building process. During the tire buildingprocess, it is important that components fit together well with aminimum of wrinkling of the tire components or trapping of air betweenthe components. If air is trapped between the uncured tire components,the tire may be defective and may have to be scrapped. During the tirebuilding process, if it appears the air has been trapped between tirecomponents, the tire builder must stitch the interfaces between theuncured elastomeric components to work any bubbles or trapped air frombetween the components. This stitching involves rolling a roller wheelalong the components, forcing the air to an edge of a component where itcan escape. The stitching process is time consuming and requires theskill of the tire builder.

[0010] As further noted by Becker, this problem is further magnified intire designs where components are rather thick compared to othercomponents. For example, when a component having a relatively squarecross-section, such as a tire bead, is positioned adjacent a more planarcomponent, such as a ply, the air may be trapped where thedifferent-shaped components interface. In tire designs wheredifferent-shaped components are necessarily placed next to each other,the problem of trapped air is even more difficult.

[0011] As further noted by Becker, in one particular extended mobilitytire design, inserts are positioned in the sidewall between the carcassplies to enable the tire to support the weight of the vehicle even ifthe tire should lose inflation pressure. These inserts are typicallythicker than the plies which lie adjacent to them and it is importantthat this tire be built without trapping air between the plies andinserts. In accordance with the present invention, an inventive tirebuilding method and drum have been designed which have features toaccommodate the special production needs of such tires. These specialfeatures will be described hereinafter and contribute to the building ofa quality tire without trapping air.

[0012] Becker therefore provides a method of building a tire comprisingthe steps of forming a liner into a cylinder, positioning first insertsto indent the liner cylindrical surface circumferentially at axiallyspaced insert locations along the axis of the cylinder, laying a firstply of reinforcing material around the cylindrical surface of the linerand first insert, positioning second inserts over the first ply at thespaced insert locations, laying a second ply of reinforcing materialover the first ply and the second inserts, positioning circular beads ateach end of the cylinder, expanding the first ply and the second ply toincrease the diameter of the cylinder between the circular beads toprovide shoulders at each end of the cylinder, turning edges of thefirst ply around the second ply over each of the beads, and positioninga belt and tread assembly around the second ply to form a precured tire.

[0013] Becker further provides a method of assembling tire components ona tire building drum having a cylindrical surface comprising the stepsof laying a liner on the surface of the drum, positioning first insertsbelow the cylindrical surface and around a drum at insert locationsspaced from each end of the drum, laying a first ply of reinforcingmaterial around the drum over the cylindrical surface of the liner andfirst insert, positioning second inserts over the first ply at theinsert locations spaced from each end of the drum, laying a second plyof reinforcing material over the first ply and the second inserts,positioning circular beads at each end of the drum, expanding the drumto increase the diameter of the cylindrical surface and provideshoulders at each end of the drum, turning edges of the first ply andthe second ply over each of the beads, positioning a belt and treadassembly around the second ply, and contracting the drum for removal ofthe assembled tire components from the drum.

[0014] Becker further provides a tire building drum which has acylindrical surface, circular grooves in the surface at insert locationsspaced from each end of the drum for positioning of first inserts belowthe surface, means for applying a first ply over the cylindricalsurface, means for applying second inserts over the first ply and thefirst inserts, means for applying a second ply over the first ply andsecond insert, means for expanding the drum providing shoulders at eachend of the drum for applying bead rings, means for turning up ends ofthe first ply around the beads, means for applying a belt and treadassembly around the second ply and means for contracting the drum toremove the assembled tire from the drum.

[0015] Commonly-owned U.S. Pat. No. 4,855,008 discloses an expandabletire building drum, especially a first stage solid pocket drum forbuilding a carcass of a radial tire, having a segmental drum (10) with aplurality of axially-extending, circumferentially spaced segments (36)with flexible connections (56) to shoulder pistons (32) at opposite endsof each segment (36). Wedge shaped bars (62) are positioned between thesegments (36) and are connected to center pistons (64) for urgingtapered side faces (80) of the bars into engagement with sloping sidefaces (78) of the segments (36). The shoulder pistons (32) and centerpistons (64) move radially outward to expand the drum. During the firststage operation, the tire reinforcing plies, beads and other componentsare assembled on the first stage drum and then the carcass is moved toanother location where it is shaped and the belt and tread applied. Inthe first stage assembly of the tire carcass it is important that thetire components be applied to contracted and expanded drum surfaceswhich are concentric and of uniform diameter along the length of thedrum. Expandible drums of different constructions have been usedheretofore; however it has been difficult to maintain a concentric drumsurface and a uniform diameter along the length of the drum in both theexpanded and contracted condition of the drum. For example, the drumsurface may be concentric and uniform in the contracted condition but isdistorted during expansion to a larger diameter. As a result, thecomponents added to the carcass on the expanded drum are not preciselyassembled which may adversely affect the uniformity of the tire.

[0016] U.S. Pat. No. 5,264,068 discloses an expandable drum includingadjustable stops for setting drum circumference. Tapering structures,each having axial slidability, are provided, and in response to a slidemove of the tapering structure, drum segments are each radially expandedor retracted. As noted therein, the tapering structure (12) is of aninner recessed frustum and is mounted over the drum shaft (10)longitudinally or axially slidable with the aid of a key (16), andhoused in the drum (14). The drum (14) is circumferentially divided intoa plurality of drum segments (17), each being like a sector, and eachsegment (17) is interiorly supported by a drum segment supporter (18).

[0017] Commonly-owned U.S. Pat. No. 4,976,804 discloses an expandable,segmental tire building drum (1) having a plurality of circumferentiallyspaced drum segments (28) radially movable by a set of links (36)pivotally connected to a pair of axially movable hub assemblies (34)slidably mounted on a drum shaft (12). Each of the segments (28) has acylindrical center portion (30) and end portions (32) with recessesproviding pockets (68) for the tire bead portions. The links (36) arepositioned between the end portions (32) providing space for large beadportions in the pockets (68) and at the same time the segments (28) areretractable to a small diameter to facilitate placing of a tire band(64) over the drum (10).

[0018] Commonly-owned U.S. Pat. No. 4,929,298 discloses a tire buildingdrum including an expandable segmental cylinder assembly and a vacuumChamber. The drum (10) has a plurality of axially-extending,circumferentially spaced segments (18). The ends of the drum are sealedto provide a vacuum chamber (76) inside the drum which is incommunication with vacuum holes (78) in a cover sleeve (48) to hold tirecomponents on the drum surface (58) during assembly of the tirecomponents.

BRIEF SUMMARY OF THE INVENTION

[0019] According to the invention, an expandable tire building drum hasalternating fixed and expanding segments (e.g., 24 of each) in a centersection of the drum. The expanding segments are axially-extending andcircumferentially spaced-apart from one another, and their end portionsare contoured (have recesses, or grooves) to accommodate tire componentssuch as sidewall inserts. Two different mechanisms for expanding thecenter section are described.

[0020] A first mechanism includes two wedge elements which are axiallymoveable away from one another to expand the center section. Rampelements associated with the expanding segments may thus be movedradially outward. Biasing elements provide a restoring force forcollapsing the center section.

[0021] A second mechanism includes two guide rings which are axiallymoveable towards one another for expanding the center section, and awayfrom one another to collapse the center section. Overlapping links areprovided between the guide rings and a base member supporting theexpanding segments.

[0022] Other objects, features and advantages of the invention willbecome apparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Reference will be made in detail to preferred embodiments of theinvention, examples of which are illustrated in the accompanying drawingfigures. The figures are intended to be illustrative, not limiting.Although the invention is generally described in the context of thesepreferred embodiments, it should be understood that it is not intendedto limit the spirit and scope of the invention to these particularembodiments.

[0024] Certain elements in selected ones of the drawings may beillustrated not-to-scale, for illustrative clarity. The cross-sectionalviews, if any, presented herein may be in the form of “slices”, or“near-sighted” cross-sectional views, omitting certain background lineswhich would otherwise be visible in a true cross-sectional view, forillustrative clarity.

[0025] Elements of the figures are typically numbered as follows. Themost significant digit (hundreds) of the reference number corresponds tothe figure number. Elements of FIG. 1 are typically numbered in therange of 100-199. Elements of FIG. 2 are typically numbered in the rangeof 200-299. Similar elements throughout the drawings may be referred toby similar reference numerals. For example, the element 199 in a figuremay be similar, and possibly identical to the element 299 in anotherfigure. Elements of the figures can be numbered such that similar(including identical) elements may be referred to with similar numbersin a single drawing. For example, each of a plurality of elementscollectively referred to as 199 may be referred to individually as 199a, 199 b, 199 c, etc. Or, related but modified elements may have thesame number but are distinguished by primes. For example, 109, 109′, and109″ are three different elements which are similar or related in someway, but have significant modifications, e.g., a tire 109 having astatic imbalance versus a different tire 109′ of the same design, buthaving a couple imbalance. Such relationships, if any, between similarelements in the same or different figures will become apparentthroughout the specification, including, if applicable, in the claimsand abstract. Sometimes, similar elements are referred to with thesuffixes -L and -R (e.g., 133L, 133R), which generally indicate left andright, as viewed in the drawing.

[0026] The structure, operation, and advantages of the present preferredembodiment of the invention will become further apparent uponconsideration of the following description taken in conjunction with theaccompanying drawings, wherein:

[0027]FIG. 1A is a schematic cross-sectional view of a tire buildingdrum, with a tire carcass being laid up thereupon, according to theprior art;

[0028]FIG. 1B is a schematic cross-sectional view of a tire buildingdrum, with a tire carcass being laid up thereupon, according to theprior art;

[0029]FIG. 2A is a perspective view of a tire building drum, accordingto the present invention;

[0030]FIG. 2B is a perspective view of a center section of the tirebuilding drum of FIG. 2A, in a collapsed position (condition), accordingto the invention;

[0031]FIG. 2C is a cross-sectional view of the center section shown inFIG. 2B, according to the invention;

[0032]FIG. 2D is a perspective view of a center section of the tirebuilding drum of FIG. 2A, in an expanded position (condition), accordingto the invention;

[0033]FIG. 2E is a cross-sectional view of the center section shown inFIG. 2D, according to the invention;

[0034]FIG. 2F is a perspective view of a typical expanding segment ofthe center section of the tire building drum of FIG. 2A, according tothe invention;

[0035]FIG. 3A is a perspective view of the center section of a tirebuilding drum, according to an embodiment of the invention;

[0036]FIG. 3B is a cross-sectional view of the center section of FIG.3A, in a fully-collapsed condition;

[0037]FIG. 3C is a cross-sectional view of the center section of FIG.3A, in a semi-expanded (or semi-collapsed) condition;

[0038]FIG. 3D is a cross-sectional view of the center section of FIG.3A, in a fully-expanded condition;

[0039]FIG. 4A is a perspective view of the center section of a tirebuilding drum, according to an alternate embodiment of the invention,showing the center section in a fully-collapsed condition;

[0040]FIG. 4B is a perspective view of the center section of a tirebuilding drum, according to an alternate embodiment of the invention,showing the center section in a fully-expanded condition;

[0041]FIG. 4C is a schematic illustration of how the linkage mechanismof the alternate embodiment of FIG. 4A and FIG. 4B works, according tothe invention;

[0042]FIG. 4D is a plan view of an alternate embodiment of a componentof the linkage mechanism, according to the invention; and

[0043]FIG. 5 is a partial cross-sectional view of a tire carcass laid upon a tire building drum, according to the invention.

DEFINITIONS

[0044] The following terms may be used throughout the descriptionspresented herein and should generally be given the following meaningunless contradicted or elaborated upon by other descriptions set forthherein.

[0045] “Apex” (also “Bead Apex”) refers to an elastomeric filler locatedradially above the bead core and between the plies and the turnup plies.

[0046] “Axial” and “axially” refers to directions that are on or areparallel to the tire's axis of rotation.

[0047] “Axial” refers to a direction parallel to the axis of rotation ofthe tire.

[0048] “Bead” refers to that part of the tire comprising an annularsubstantially inextensible tensile member, typically comprising a cableof steel filaments encased in rubber material.

[0049] “Belt structure” or “reinforcement belts” or “belt package”refers to at least two annular layers or plies of parallel cords, wovenor unwoven, underlying the tread, unanchored to the bead, and havingboth left and right cord angles in the range from 18 to 30 degreesrelative to the equatorial plane of the tire.

[0050] “Breakers” or “tire breakers” refers to a belt or belt structureor reinforcement belts.

[0051] “Carcass” refers to the tire structure apart from the beltstructure, tread, undertread over the plies and the sidewalls, butincluding the beads, plies, and, in the case of EMT or runflat tires,the wedge inserts sidewall reinforcements.

[0052] “Casing” refers to the carcass, belt structure, beads, sidewallsand all other components of the tire excepting the tread and undertread.

[0053] “Centerplane” refers to a plane intersecting a line which isnormal to the plane at a point which is midway between two other pointson the line. The line may be an axis of a cylindrical member, such as atire building drum. A finished tire has a centerplane which is the“equatorial plane” of the fire.

[0054] “Chafer” refers to reinforcing material (rubber alone, or fabricand rubber) around the bead in the rim flange area to prevent chafing ofthe tire by the rim parts.

[0055] “Chipper” refers to a narrow band of fabric or steel cordslocated in the bead area whose function is to reinforce the bead areaand stabilize the radially inwardmost part of the sidewall.

[0056] “Circumferential” refers to circular lines or directionsextending along the perimeter of the surface of the annular treadperpendicular to the axial direction, and can also refer to thedirection of sets of adjacent circular curves whose radii define theaxial curvature of the tread, as viewed in cross section.

[0057] “Cord” refers to one of the reinforcement strands, includingfibers or metal or fabric, with which the plies and belts arereinforced.

[0058] “Crown” or “tire crown” refers to the tread, tread shoulders andthe immediately adjacent portions of the sidewalls.

[0059] “EMT tire” refers to Extended Mobility Technology and EMT tirerefers to a tire which is a “runflat”, which refers to a tire that isdesigned provide at least limited operational service under conditionswhen the tire has little to no inflation pressure.

[0060] “Equatorial plane” refers to a the plane perpendicular to thetire's axis of rotation and passing through the center of its tread, ormidway between the tire's beads.

[0061] “Gauge” refers generally to a measurement, and often to athickness dimension.

[0062] “Inner liner” refers to the layer or layers of elastomer or othermaterial that form the inside surface of a tubeless tire and thatcontain the inflating gas or fluid within the tire. Halobutyl, which ishighly impermeable to air.

[0063] “Insert” refers to the crescent-shaped or wedge-shapedreinforcement typically used to reinforce the sidewalls of runflat-typetires; it also refers to the elastomeric non-crescent-shaped insert thatunderlies the tread; it is also called a “wedge insert.”

[0064] “Lateral” refers to a direction parallel to the axial direction.

[0065] “Meridional profile” refers to a tire profile cut along a planethat includes the tire axis.

[0066] “Ply” refers to a cord-reinforced carcass reinforcing member(layer) of rubber-coated radially deployed or otherwise parallel cords.

[0067] “Pneumatic tire” refers to a laminated mechanical device ofgenerally toroidal shape (usually an open-torus) having two beads, twosidewalls and a tread and made of rubber, chemicals, fabric and steel orother materials.

[0068] “Shoulder” refers to the upper portion of sidewall just below thetread edge.

[0069] “Sidewall” refers to that portion of a tire between the tread andthe bead.

[0070] “Tire axis” refers to the tire's axis of rotation when the tireis mounted to a wheel rim and is rotating.

[0071] “Tread cap” refers to the tread and the underlying material intowhich the tread pattern is molded.

[0072] “Turn-up end” refers to a portion of a carcass ply that turnsupward (i.e., radially outward) from the beads about which the ply iswrapped.

DETAILED DESCRIPTION OF THE INVENTION

[0073] Generally speaking, a conventional process for making aradial-ply automobile tire includes an intermediate step of disposingtwo annular inextensible beads, each comprising a cable of steelfilaments encased in green rubber, over the other components of a green(“green” meaning as yet uncured and still tacky) tire carcass on a tirebuilding drum. An annular cross-sectionally triangular rubber fillercalled an “apex” may be added. Portions of the ply components thatextend beyond the beads are then turned up around the beads, forming“turn-ups”. Then, the green carcass is typically removed from the tirebuilding drum and mounted on a “second stage machine” where it isinflated (reshaped) to a toroidal shape, and its radially-outer surfaceis pressed against a tread and belt package. In subsequent steps, thegreen carcass is stitched (rolled with a roller) to remove air pocketsand adhere internal surfaces together. The resulting assembly isinserted into a mold (vulcanizing press) to cure under heat (typically350 degrees Fahrenheit) and pressure to become a finished tire.

[0074]FIG. 1A corresponds generally to FIG. 9 of Becker, and illustrates(schematically, and in a greatly simplified manner) an exemplary tirebuilding drum 102 of the prior art. The drum 102 is generallycylindrical, having two ends 102 a and 102 b, an axis of rotation 104extending between the two ends, and a cylindrical outer surface 106. Acenterplane (CP) is indicated on the drawing, and is generally a planewhich bisects a carcass being laid up on the tire building drum.

[0075] In a typical (again, greatly simplified, for illustrativeclarity) tire buildup, an inner liner 108 is applied on the surface ofthe drum 102, and two tire sidewall insert components (“inserts”) 110 aand 110 b (collectively referred to as “110”) are disposed atlongitudinally (axially) spaced apart positions on the inner liner 108,as shown. Next, a first ply 112 is disposed over the inner liner 108 andinserts 110. This results in a green tire carcass having a nominallycylindrical shape. However, as is evident from the illustration of FIG.1A, the addition of the sidewall inserts 110 between the inner liner 108and the ply 112 causes there to be two “bumps” (protrusions), which areregions of increased outside diameter (“OD”), in the outer surface ofthe carcass. As can be seen, these bumps protrude significantly upwardlyfrom the outer surface of the tire building drum and create significantprotrusions 18 in these areas. Subsequent tire components such as asecond carcass ply are difficult to force into such a nonplanar contour.At the locations of the protrusions, air can be trapped within the tire,leading to the aforementioned problems.

[0076] Next, two beads 114 a and 114 b (collectively “114”) are added tothe tire carcass. Each bead 114 is a substantially inextensible circularhoop, having an inside diameter (“ID”) which is substantially equal toor preferably only slightly greater than the OD of the ply 112 (in areasother than where there are bumps). The beads 114 are shown as beingslightly axially outboard of the inserts 110, and are shown as having around (versus hexagonal) cross-section for sake of illustrative clarity.A second ply (not shown) may be added to the carcass, and the outer endportions of the carcass may be turned up. Finally the carcass may betransferred to another (second stage) machine for adding a treadpackage, etc.

[0077]FIG. 1B corresponds generally to FIGS. 2-7 of Becker, andillustrates an alternate embodiment of an exemplary tire building drum122 of the prior art. The drum 122 is generally cylindrical, having twoends 122 a and 122 b, an axis of rotation 124, and a generallycylindrical outer surface 126. The drum 122 differs from the drum 102 ofFIG. 1A primarily by virtue of having annular recesses (pockets,grooves) 136 a and 136 b (collectively referred to as “136”) in itsouter surface at longitudinal (axial) positions corresponding to thepositions of and related to the dimensions of inserts 130 a and 130 b(collectively referred to as “130”) and extending about thecircumference of the drum 122. In this example, the inner liner 128 isapplied to the surface 126 of the drum 122. Then the inserts 130 areapplied, and fit (nestle) down into the recesses 136. Then a ply 132 isapplied. This results in a green tire carcass having a substantiallycylindrical shape. In contrast to the tire carcass formed in FIG. 1A,the addition of the inserts 130 between the inner liner 128 and the ply132 does not cause there to be two “bumps” in the outer surface of thecarcass. Since there are substantially no bumps, and the outer surfaceof the tire carcass being laid up is substantially cylindrical, having asubstantially uniform OD, it is (among other things) possible to mounttwo beads 134 a and 134 b (collectively referred to as “134”) onto thecarcass by sliding them both on from one end (e.g., 122 a) of the drum122.

[0078]FIGS. 2A through 2D illustrate, generally, the tire building drum202 of the present invention. The drum 200 is generally cylindrical,having two ends 202 a and 202 b, an axis of rotation 204 extendingbetween the two ends, and a cylindrical outer surface 206. The drum 202has an overall axial length “L” between the two ends. A spindle (or drumsupport shaft) extends along the axis 204 and has an end 208 a extendingfrom the end 202 a of the drum 202, and an end 208 b extending from theend 202 b of the drum 202.

[0079] The drum 202 has a center section 220 which is generallycylindrical, and centered about the axis 204. The center section 220 hasa width (more properly, axial length) of L_(C). The drum 202 has a firstend section 222 which is coaxial with the center section 220, and whichis disposed axially at one end of the center section 220. The drum 202has a second end section 224 which is coaxial with the center section220, and which is disposed axially at an opposite end of the centersection 220. The two end sections 222 and 224 are, for purposes of thepresent invention, substantially identical to (i.e., mirror images of)one another, each having an axial length of (L-L_(C))/2. The endsections 222 and 224 are axially-outward of the center section 220. Thedrum, more significantly the center section 220 of the drum, has acenterplane (compare CP, FIG. 1A), which is a plane intersecting theaxis 204 midway between the ends of the center section (typically alsomidway between the ends 202 a, 202 b) of the overall drum. The axis 204is, by definition, normal to the centerplane.

[0080] The center section 220 is circumferentially segmented, having aplurality of elongate fixed segments 226 alternating with a likeplurality of elongate expanding segments 228. As best viewed in any ofFIGS. 2B-2D, there are suitably 24 (twenty four) fixed segments 226alternating with 24 (twenty four) expanding segments 228. The expandingsegments 228 are axially-extending and circumferentially spaced from oneanother, and end portions of each is contoured to have annular recesses(pockets, grooves) 236 a and 236 b (collectively referred to as “236”;compare 136) in its outer surface at longitudinal (axial) positionscorresponding to the positions of and related to the dimensions ofsidewall inserts (not shown, compare 130) which will be applied duringthe carcass layup process, described hereinabove. The pockets 236 canbest be viewed in FIG. 2F, wherein can also be viewed two turnup bladder(not shown) anchor points 238 a and 238 b in the outer surface of theexpanding segment. In FIGS. 2F and 5A, it is seen that end portions ofthe expanding segments 238, 538 are contoured to have pockets 236, 536for receiving components (e.g., sidewall inserts) of a tire carcassbeing laid up on the drum.

[0081] The fixed segments 226 are elongate, generally rectangular incross-section and have a length substantially equal to L_(C). The fixedsegments 226 typically have a fixed width or have a width proportionalto the number of total segments. The expanding segments 228 are alsoelongate, generally rectangular in cross section, and have a lengthsubstantially equal to L_(C).

[0082] It is within the scope of the invention that there are anysuitable number of fixed and expanding segments, for example, ratherthan twenty four of each, anywhere from eighteen to thirty of each. Itis also within the scope of the invention that the number of fixedsegments is not exactly equal to the number of expanding segments. It isalso within the scope of the invention that the expanding segments donot all have the exact same width. The same applies to the fixedsegments. Selected ones of the fixed and/or expanding segments can be“special purpose” segments, such as for communicating vacuum to an innerliner being laid up on the drum.

[0083] The center section 220 is expandable, between a collapsed (orretracted, or contracted) condition, shown in FIGS. 2B and 2C and anexpanded (or extended) condition (or “fully” expanded position), shownin FIGS. 2D and 2E. Mechanisms for effecting expansion and collapse ofthe center section 220 are described hereinbelow, and accommodatepartially expanding the center section to one (or more) “semi-expanded”positions. Generally, each of said expanding segments 228 is expandablefrom a first radius in the a collapsed condition of said drum to asecond, greater radius in an expanded condition of said drum.

[0084] “Dual Cone” Mechanism For Expanding/Collapsing The Center Section

[0085]FIGS. 3A-3D illustrate the major components of an expandablecenter section 320 (compare 220) of a tire building drum, according toan embodiment of the invention. In the view of FIG. 3A, one of aplurality (e.g., 24) of expanding segments 328 (compare 228) is shown,and a corresponding one of a plurality (e.g., 24) of fixed segments 326(compare 226) is shown. In FIGS. 3B-3D, the expanding segment 328 isshown, but not the fixed segment 326, for illustrative clarity. Aspindle 308 is illustrated highly schematically in FIGS. 3B-3D, and isomitted from FIG. 3A, for illustrative clarity. A base member 346 forthe fixed segment 326 is shown in FIG. 3A only, for illustrativeclarity. A base (ramp) element 348 for the expanding segment 328 is bestviewed in FIGS. 3B-3D.

[0086] Two guide elements (flanges) 340 a and 340 b (collectivelyreferred to as “340”) are disposed at axially spaced apart positions ona spindle 308 (compare 208) which extends along the axis 304. Theflanges 340 are suitably in the form of generally planar discs which arecentered on the axis 304, and are parallel with one another. Each flange340 has an inner surface which faces, and is parallel with the innersurface of the other flange 340. The flanges 340 are essentially fixedto the spindle 308, which means that they will rotate with the spindle,and that they are at a fixed axial distance apart from one another. Theflanges 340 are preferably centered about the centerplane. The flanges340 are a distance apart which, as illustrated, is less than the lengthL_(C) of the segments 326, 328.

[0087] The inner surfaces of the flanges 340 a and 340 b are providedwith a plurality of radially-extending grooves 342 a and 342 b,respectively. A given groove 342 a on the guide plate 340 a correspondsto, and is at the same circumferential position on the spindle 308 as, agiven groove 342 b on the guide plate 340 b. These two given grooves 342a, 342 b form a given pair of grooves and, for example, there are 24(twenty four) pairs of grooves, spaced at even intervals about the innersurfaces of the flanges 340. Each of these given pairs of grooves 342 a,342 b function as a track for guiding an expanding segment supportmember (ramp element) 348 associated with an expanding segment 328,radially inward and outward, as discussed hereinbelow.

[0088] Each expanding segment 328 has a ramp element 348 associatedtherewith. (For 24 expanding segments 328, there are 24 ramp elements348.) The ramp element 348 is essentially a flat planar element havingfour edges (sides)—a top edge for supporting the expanding segment 328,a bottom “ramped” edge which functions as a ramp surface for being actedupon by two movable wedge elements 358 (described in greater detailhereinbelow), a first side edge which rides in the groove 342 a of agiven groove pair, and a second side edge which rides in the groove 342b of the given groove pair. Preferably, the ramp element 348 is separatefrom the expanding segment 328, but it is within the scope of theinvention that it is integrally formed therewith. In the case that theramp element 348 is not formed integrally with the expanding segment328, the expanding segment 328 may be attached in any suitable manner tothe ramp element 348.

[0089] The inner surfaces of the flanges 340 a and 340 b are alsoprovided with a plurality of radially-extending grooves 343 a and 343 b,respectively. Each of the radially-extending grooves 343 a and 343 b areinterspersed between the radially-extending grooves 342 a and 342 b Theradially-extending grooves 343 a and 343 b are shorter than theradially-extending grooves 342 a and 342 b. A given groove 343 a on theguide plate 340 a corresponds to, and is at the same circumferentialposition on the spindle 308 as, a given groove 343 b on the guide plate340 b. These two given grooves 343 a, 343 b form a given pair of groovesand, for example, there are 24 (twenty four) pairs of grooves, spaced ateven intervals about the inner surfaces of the flanges 340. Each ofthese given pairs of grooves 343 a, 343 b function as a track forreceiving and securing a fixed segment support member 346 associatedwith a fixed segment 326, as discussed hereinbelow. The base member 346is essentially a rectangular block, extending between grooves of theflanges and having four edges (sides)—a top edge for supporting thefixed segment 326, a first side edge which fits in a groove 343 a, asecond side edge which fits in a groove 343 b, and a generally flatbottom edge. In the case of 24 (twenty four) fixed segments 326, thereare 24 (twenty four) base members 346 extending between 24 pairs ofgrooves 343 a, 343 b. (The side edges of the base members are receivedin the grooves.) This accounts for the total overall number of groovesin each flange (and the total overall number of groove pairs in theflanges) being 48 (forty eight)—24 pairs of grooves for guiding theexpanding segments 328 as they move radially in and out, and 24 pairs ofgrooves for locating the fixed segments 326 between the expandingsegments 328 even though radial movement is not contemplated or required(to the contrary, the fixed segments are supposed to remain at selectedradial positions). Preferably, the base member 346 is separate from thefixed segment 326, but it is within the scope of the invention that itis integrally formed therewith. In the case that the base member 346 isnot formed integrally with the fixed segment 326, the fixed segment 326may be attached in any suitable manner to the base member 346.

[0090] In FIG. 3A, it can be seen that the fixed segment 326 has anaxial length which is substantially the same as the axial length of theexpanding segment 328, and that the axial length L_(C) of both isgreater than the spacing between the two flanges 340, and that they are“centered” with regard to the flanges 340 (and the centerplane).

[0091] Two biasing members 338 a and 338 b (collectively referred to as“338”) are provided. One of the biasing members, 338 b) is shown inphantom in FIG. 3A. The other of the biasing members, 338 a, is shown inphantom in FIGS. 3B-3D, for illustrative clarity. The biasing members338 are disposed at axially spaced apart positions about the spindle308, and are suitably in the form of rubber bands extending throughcorresponding holes 342 a and 342 b in each of the ramp elements 348.These rubber bands 338 exert a “collapsing” radial force on the rampelements 348 in the direction of the axis 304. As shown in FIG. 3A, thebase members 346 for the fixed segments 326 may also be provided withholes 344 a and 344 b, through which the rubber bands 338 extend.

[0092] Two tapered (wedge) elements 358 a and 358 b (collectivelyreferred to as “358”) are disposed at axially spaced apart positions onthe spindle 308 (on either side of the centerplane). The wedge elements358 are suitably in the form of generally planar discs (rings, sincethey are discs with a hole in the middle) which are centered on the axis304, and are parallel with one another. The outer faces of the wedgeelements 358 are tapered. Therefore, the wedge elements 358 arefrustroconical, and may be referred to as “cones”, or “cone-shapedelements”, or “conical elements”. The wedge elements 358 are not fixedto the spindle 308. Rather, although they may be keyed (or splined) tothe spindle so that they will rotate with the spindle, they are free tomove axially (traverse) along the spindle, towards and apart form oneanother, from a minimum distance (essentially touching one another), toa maximum distance from one another, remaining parallel with each otherirrespective of the axial distance form one another.

[0093] In FIG. 3B, the center section 320 is shown in its collapsed (or“fully-collapsed”) position. In this position, the wedge elements 358are close together (e.g., essentially zero distance apart from oneanother, with their bases touching, or nearly touching), and the rampelement 348 and, consequently, the expanding segment 328 is at itsminimal radial distance from the axis 304. In other words, the diameterof the center section 320 is at a minimum in this collapsed (retracted)position. In this collapsed position, the outer surface of the centersection 320 has substantially the same diameter as that of the outersurfaces 306 (compare 206) of adjacent end sections 322 and 324 (compare222, 224). In this collapsed position, a tire component, such as theinner liner (e.g., 504, see below) of a tire carcass, may be applied.

[0094] In FIG. 3C, the center section 320 is shown in its semi-expandedposition. In this position, the wedge elements 358 are spread apart fromone another (but not as far apart as they are capable of spreading), andthe ramp element 348 and, consequently, the expanding segment 328 is ata greater radial distance from the axis 304. In other words, thediameter of the center section 320 is now larger, or expanded. In thissemi-expanded position, the outer surface of the center section 320 hasa slightly greater diameter than that of the outer surfaces 306 (compare206) of adjacent end sections 322 and 324 (compare 222, 224). In thissemi-expanded position, a tire component, such as the ply (e.g., 508,see below) of a tire carcass, may be applied.

[0095] In FIG. 3D, the center section 320 is shown in its fully-expandedposition. In this position, the wedge elements 358 are spread (havemoved) farther apart from one another (essentially as far apart as theyare capable of spreading, their bases far apart from one another), andthe ramp element 348 and, consequently, the expanding segment 328 is atan even greater radial distance from the axis 304. In other words, thediameter of the center section 320 is now even larger, or more expanded.In this fully-expanded position, the outer surface of the center section320 has a much greater diameter than that of the outer surfaces 306(compare 206) of adjacent end sections 322 and 324 (compare 222, 224).Concurrently with the drum in the fully-expanded position, separatelyactuated bead locks (not shown) cause the beads to be firmly set. Next,the ends of the carcass can then be turned up, in a final step ofcarcass construction. Then, the center section 320 of the drum can bepartially collapsed (e.g., returned to a semi-expanded position), thebead locks collapsed and the carcass can be removed for furtherprocessing, such as the application of a tread package in a second stagetire building machine.

[0096] The two wedge elements 358 are in the form of cones (moreaccurately, frustroconical), disposed coaxially (having the same axis)with their bases opposing (facing) one another, and their apexes (albeittruncated) remote from one another. It is preferred that the two wedgeelements 358 remain at all times, throughout their range of axialmovement, equidistant from the centerplane of the center section 320 ofthe drum. The bottom edge (inner surface) of the ramp element 348 isV-shaped, with two intersecting ramp surfaces, one for each of the wedgeelements 358. In this manner, forces exerted by the wedge elements 358are evenly distributed along the length of the ramp element 348 and,consequently, the expanding segment 328. The angle along the outer edges(faces) of the wedge elements 358, and the corresponding angle along theinner edges (surfaces) of the ramp elements 348 is suitably between 20degrees and 45 degrees, such as approximately 30 degrees, moreparticularly such as 33 degrees, with respect to the axis, or moreparallel to the axis than perpendicular thereto. This angle, of course,remains constant irrespective of the axial positions of the wedgeelements 358. As the wedge elements 358 move farther apart from oneanother, the expanding segments 328 are urged radially outward from theaxis 304.

[0097] The expanding segment 328 has a length L_(C). The fixed segment326 has a length substantially equal to L_(C). The flanges 340 arespaced apart a distance less than the length L_(C). In the illustrationsof FIGS. 3A-3D, a total of 48 (forty eight) grooves 342 are shown ineach flange 340. As discussed hereinabove, 24 of these grooves on eachflange form a given pair of grooves for guiding the ramp elements 348 asthey are forced radially outward and return radially inward. As bestviewed in FIG. 3A, the base member 346 extends between intermediatepairs of grooves 342 in the flanges 340. Also, the base members 346 mustpass over (by, through) the wedge elements 358. Therefore, the wedgeelements 358 have 24 notches 356 at evenly spaced circumferentialpositions about the outer surface of their respective bases forreceiving a bottom edge of the base member 346 as it passes by. Thisserves to ‘lock’ the wedge elements 358 in fixed circumferentialpositional relationship with respect to the flanges 340, while allowingthe wedge elements 358 to move axially back and forth in the spacebetween the flange elements 340.

[0098] It is therefore seen that expansion of the center section 320 ofa tire building drum can be accomplished using a traversing dual conemechanism which exerts radial forces on the expanding segments 328 whichare symmetrical about the centerplane of the drum (i.e., of the centersection 320). With only one tapering structure, such as in U.S. Pat. No.5,264,068, such symmetry cannot be accomplished. Applying expandingforces, with symmetry about the centerplane, can be critical toachieving uniformity in the layup of a tire carcass.

[0099] Although not shown, any suitable mechanism can be used for movingthe tapered wedge elements axially 358 outward to effect expansion ofthe center section 320, and axially inward (towards one another) forpermitting retraction of the center section 320.

[0100] Suitable dimensions for the center section 320 are:

[0101] diameter collapsed=400 mm

[0102] diameter semi-expanded=420 mm

[0103] diameter fully-expanded 476 mm (expansion of 76 mm)

[0104] minimum center section width (L_(C)) of 250 mm

[0105] When the center section 320 is collapsed, the surface of the drumis substantially continuous, smooth, uninterrupted (flat), and this isadvantageous for innerliner application. It is within the scope of theinvention that means for providing a vacuum, through selected ones ofthe segments (either fixed or expanding), to the surface of the drum, tohold the innerliner securely thereon, be provided, in any suitablemanner. When the center section is semi-expanded, the surface is alsosubstantially flat, such as would be advantageous for ply application.

[0106] “Overlapping Linkage” Mechanism For Expanding/Collapsing TheCenter Section

[0107]FIGS. 4A-4C illustrate an alternate embodiment of a mechanism forexpanding and collapsing the center section of a tire building drum.Whereas the embodiment of FIGS. 3A-3D used a dual cone and rampmechanism for expansion, and rubber bands for collapsing the centersection, in this embodiment the linkage is capable of both expanding andcontracting the expanding segments of the center section.

[0108]FIGS. 4A-4C illustrate the major components of an expandablecenter section 420 (compare 320) of a tire building drum, according toan alternate embodiment of the invention. In the illustration of FIG.4C, one of a plurality (e.g., 24) of expanding segments 428 (compare328) is shown. In the views of FIGS. 4A and 4B, the expanding segment isomitted, for illustrative clarity. It will be understood that thegeneral alternating arrangement of fixed and expanding segments issubstantially the same in this embodiment as in the previously-describedembodiment. In describing this embodiment, the fully-collapsed positionof the center section 420 is shown in FIG. 4A, and the fully-expandedposition of the center section 420 is shown in FIG. 4B. It will beunderstood that in this, as in the previous embodiment, the drum may beexpanded (or collapsed) to any position (diameter) betweenfully-collapsed and fully-expanded. A spindle (compare 308) extendsalong the axis 404 of the drum, but it omitted, for illustrativeclarity. Although not shown, the center section is provided with fixedsegments (e.g., 326), in the same (or similar) manner as was thepreviously-described embodiment.

[0109] Two flanges 440 a and 440 b (collectively referred to as “440”;compare 340) are disposed at axially spaced apart positions on thespindle. The flanges 440 are substantially similar to the flanges 340 ofthe previous embodiment, and are suitably in the form of generallyplanar discs which are centered on the axis (304), and are parallel withone another. Each guide element 440 has an inner surface which faces,and is parallel with the inner surface of the other guide element 440.The flanges 440 are essentially fixed to the spindle (308), which meansthat they will rotate with the spindle (308), and that they are at afixed axial distance apart from one another.

[0110] The inner surfaces of the flanges 440 a and 440 b are providedwith a plurality of radially-extending grooves 442 a and 442 b, and 443a and 443 b respectively. Again, this is comparable to the grooves 342 aand 342 b, and 343 a and 343 b, respectively of the previously-describedembodiment. A given groove 442 a on the guide plate 440 a correspondsto, and is at the same circumferential position on the spindle as, agiven groove 442 b on the guide plate 440 b. These two given grooves 442a, 442 b form a pair of grooves and, for example, there are 24 pairs ofgrooves, spaced at even intervals about the inner surfaces of theflanges. Each pair of grooves functions as a track for guiding anexpanding segment support, or base (support) element 448 (compare 348)as it moves radially inward or outward from the axis, as discussedhereinbelow. Further, a given groove 443 a on the guide plate 440 acorresponds to, and is at the same circumferential position on thespindle as, a given groove 443 b on the guide plate 440 b. These twogiven grooves 443 a, 443 b form a pair of grooves and, for example,there are 24 pairs of grooves, spaced at even intervals about the innersurfaces of the flanges. Each pair of grooves functions as a track forsecuring base (support) element 446 (compare 346) which is secured tothe fixed segments, as discussed hereinbelow.

[0111] Each expanding segment 428 has a support element 448 associatedtherewith. (For 24 expanding segments, there are 24 base members.) Thesupport element 448 is essentially a flat planar element having fouredges (sides)—a top edge for supporting the expanding segment 328, afirst side edge which rides in the groove 442 a of a given groove pair,and a second side edge which rides in the groove 442 b of the givengroove pair. The support element 448 also has a bottom edge, but theshape of that edge is of no particular importance (as contrasted withthe bottom edge ramp surface of the ramp element 348). Preferably, thesupport element 448 is separate from the expanding segment 428, but itis within the scope of the invention that it is integrally formedtherewith. In the case that the support element 448 is not formedintegrally with the expanding segment 428, the expanding segment 428 maybe attached in any suitable manner to the support element 448.

[0112] Two guide rings (hubs) 458 a and 458 b (collectively referred toas “458”) are disposed at axially spaced apart positions on the spindle(on either side of the centerplane). The guide rings 458 are suitably inthe form of generally planar discs (rings, since they are discs with ahole in the middle) which are centered on the axis 404, and are parallelwith one another. The guide rings 458 are not fixed to the spindle.Rather, although they may be keyed (or splined) to the spindle so thatthey will rotate with the spindle, they are free to move axially alongthe spindle, towards and apart form one another, from a minimum distance(essentially touching one another), to a maximum distance from oneanother, remaining parallel with each other irrespective of the axialdistance form one another.

[0113] An overlapping linkage mechanism 460 is provided between theguide rings 458 and the support element 448. The linkage mechanismcomprises:

[0114] a first elongate link 462 having an end pivotally attached to aone (458 a; left, as viewed) of the guide rings 458, and an opposite endpivotally attached adjacent (near) a one (right, as viewed) end of thesupport element 448; and

[0115] a second elongate link 464 having an end pivotally attached tothe other (458 b; right, as viewed) of the guide rings 458, and anopposite end pivotally attached adjacent (near) an opposite (left, asviewed) end of the support element 448.

[0116] The links 462 and 464 overlap each other (cross over oneanother), but are not pivotally attached to each other, as would be thecase with a “scissors” type linkage, nor are they parallel to eachother, as would be the case with a two-link “toggle” type linkage.

[0117] In FIG. 4A (compare FIG. 3B) the center section 420 is shown inits collapsed (or “fully-collapsed”) position. In this position, theguide rings 458 are spread far apart from one another (essentially asfar apart as they are capable of spreading), and the support element 448and, consequently, the expanding segment 428 is at its minimal radialdistance from the axis 404. In other words, the diameter of the centersection 420 is at a minimum in this collapsed position. In thiscollapsed position, the outer surface of the center section 420 hassubstantially the same diameter as that of the outer surfaces (306) ofadjacent end sections (322, 324). In this collapsed position, the innerliner of a tire carcass may be applied.

[0118] In FIG. 4B (compare FIG. 3D), the center section 420 is shown inits fully-expanded position. In this position, the guide rings 458 areclose together (e.g., essentially zero distance apart from one another),and the support element 448 and, consequently, the expanding segment 428is at its greatest greater radial distance from the axis 404. In otherwords, the center section 420 is now fully-expanded. In thisfully-expanded position, the outer surface of the center section 420 hasa much greater diameter than that of the outer surfaces (306) ofadjacent end sections (e.g., 222, 224). Concurrently with the drum inthe fully-expanded position, separately actuated bead locks (not shown)cause the beads to be firmly set. Next, the ends of the carcass can thenbe turned up, in a final step of carcass construction. Then, the centersection 420 of the drum can be partially collapsed (e.g., returned to asemi-expanded position), the bead locks collapsed and the carcass can beremoved for further processing, such as the application of a treadpackage in a second stage tire building machine.

[0119] In the collapsed condition (FIG. 4A), the links 462 and 464 areboth nearly parallel to the axis 404. For example, at an angle of 19.6degrees with respect thereto. In the expanded condition (FIG. 4B), thelinks 462 and 464 are at an angle approximately halfway between parallelto and perpendicular to the axis 303, such as at an angle of 46.2degrees with respect thereto. This provides for a relatively compactmechanism with a good operating range.

[0120] Although not shown, the center section can be expanded to anydiameter between collapsed and fully-expanded, as determined by thespacing of the guide rings 458 from one another. For example, in asemi-expanded position, the ply of a tire carcass may be applied. It ispreferred that the two guide rings 458 remain equidistant from thecenterplane of the center section 420 of the drum while they are movingin their range of positions. In this manner, forces are evenly(symmetrically) distributed along the length (L_(C)) of the supportelement 448 and the expanding segment 428.

[0121] In this example, with the overlapping linkage, the relationshipbetween guide ring spacing and center section diameter is inverse—thecloser the guide rings are to one another, the greater the diameter ofthe center section. In the previous example (wedge/ramp), therelationship between guide rings spacing and center section diameter isdirect—the closer the guide rings are to one another, the lesser thediameter of the center section. In either case however, the diameter ofthe center section 320 and 420 is proportional (directly or inversely,respectively) to the spacing between the wedge elements 358 or guiderings 458, respectively.

[0122] The overlapping linkage mechanism of FIGS. 4A-4C is superior to atoggle linkage, for example as shown in the aforementioned U.S. Pat. No.4,929,298 with regard to being able to apply forces to the expandingsegment in a manner which is symmetrical about the centerplane,throughout the range of expansion for the drum. A toggle linkage,wherein two links move in unison parallel to one another, is inherentlynot symmetrical about the centerplane. This symmetry, as in the previous(wedge) embodiment, can be of profound significance in achievinguniformity in the layup of the tire carcass.

[0123] The overlapping linkage embodiment of FIGS. 4A-4C is similar tothe wedge/ramp embodiment of FIGS. 3A-3D, in the following regards:

[0124] both are for expanding and collapsing a center section (220, 320,420) of a tire building drum;

[0125] both act upon expanding segments (228, 328, 428) of the centersection;

[0126] both do not act upon the fixed segments (226, 326, 426) of thecenter section;

[0127] both employ flanges (340, 440) which have grooves (342, 442) forguiding a ramp element (348) or support element (448) which supports theexpanding segment (328, 428);

[0128] both have elements (358, 458) which move axially to effect theexpansion/collapse of the center section;

[0129] both exert expanding forces on the expanding segments in a mannerwhich is symmetrical about the centerplane.

[0130] The symmetry of forces exerted (urged) upon the expandingsegments, about the centerplane, is non-trivial. As mentioned above, acarcass ply which is lopsided (longer cords on one side of the tire thanthe other side) can cause a variety of tire nonuniformity problemsincluding static imbalance and radial force variations. The presentinvention addresses one potential source of such nonuniformities—namely,imprecise (e.g., non-cylindrical) expansion of the drum.

[0131] In both embodiments, when the center section (320, 420) iscollapsed, the surface of the drum is substantially continuous, smooth,uninterrupted (flat), and this is advantageous for innerlinerapplication. It is within the scope of the invention that means forproviding a vacuum, through selected ones of the segments (either fixedor expanding), to the surface of the drum, to hold the innerlinersecurely thereon, be provided, in any suitable manner. When the centersection is semi-expanded, the surface is also substantially flat, suchas would be advantageous for ply application. Both embodiments can use aroller screw system for center section expansion. The mechanism formoving the wedges 358 or guide rings 458 depends largely on otherfactors present in the overall drum construction, and can be adapted ona case-by-case basis.

[0132] The overlapping linkage embodiment of FIGS. 4A-4C is differentfrom the wedge/ramp embodiment of FIGS. 3A-3D, in the following regards:

[0133] in the wedge/ramp embodiment, rubber bands (338) are used tocollapse the center section (320);

[0134] in the overlapping linkage embodiment, the links (462, 464)themselves effect collapse of the center section;

[0135] in the wedge/ramp embodiment, the center section (320) expandswhen the wedges (358) move axially apart, and retracts when the wedges(358) move together.

[0136] in the overlapping linkage embodiment, the center section (420)expands when the guide rings (458) move closer together, and retractswhen the guide rings (358) move farther apart.

[0137] The overlapping linkage design tends to provide more expansionrange in a narrower width (L_(C)), allowing the minimum drum width toshrink, for example from 250 mm (for the wedge embodiment) to 200 mm(for the linkage embodiment) .

[0138] Some exemplary dimensions for the center section (420 of thelinkage embodiment are presented in the following table. Tire Size (in.)14 15 16 17 18 19 20 Rim Dia (in.) 14 15 16 17.2 18.2 19.2 20.2 Expanded(mm) 391 416 441 472 497 523 548 Intermediate (mm) 338 364 390 420 444468 493 Collapsed (mm) 308 334 350 380 404 428 453 expansion (mm) 83 8291 92 93 95 95

[0139]FIG. 4D illustrates an alternate embodiment of a support element448′ which is provided with two holes 442 a and 442 b (compare 342 a and342 b) for receiving biasing members comparable to the biasing members338 shown in FIGS. 3A-3D. The biasing members, suitably in the form ofrubber bands, would exert a “collapsing” radial force on the supportelement 448′.

[0140] Extended Mobility Tires

[0141]FIG. 5 is a partial cross-sectional view of an exemplary tirecarcass as it is laid up on a tire building drum, according to theinvention. An end of an expanding segment 528 is shown. First, First, acenter sleeve 502 is installed on the surface of the drum and extendsover the expanding segment 528. . An upper turnup bladder 503 and alower turnup bladder 505 extends beyond the drum. The tire carcasscomprises the following major components, in the following order:

[0142] an innerliner 504;

[0143] a first sidewall insert (pillar) 506;

[0144] a first ply (ply 1) 508;

[0145] a second sidewall insert (post) 510;

[0146] a second ply (ply 2) 512;

[0147] a bead 514;

[0148] an apex 516;

[0149] a chafer 518; and

[0150] a sidewall 520.

[0151] Other components, such as chipper, gum toeguard and fabrictoeguard may be added to the carcass, as may be desired, but form nospecial part of the present invention.

[0152] Although the invention has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character—it beingunderstood that only preferred embodiments have been shown anddescribed, and that all changes and modifications that come within thespirit of the invention are desired to be protected. Undoubtedly, manyother “variations” on the “themes” set forth hereinabove will occur toone having ordinary skill in the art to which the present invention mostnearly pertains, and such variations are intended to be within the scopeof the invention, as disclosed herein.

1. A tire building drum having an axis and a centerplane intersectingthe axis, comprising: a plurality of axially extending,circumferentially spaced-apart expanding segments, each of saidexpanding segments being expandable from a first radius in a collapsedcondition of said drum to a second radius in an expanded condition ofsaid drum; a pair of flanges centered about the axis at a fixed distancefrom one another; a plurality of ramp elements, each supporting anexpanding segment, disposed between the flanges and radially moveablebetween the flanges; at least one conical element disposed coaxiallybetween the pair of flanges, axially moveable therebetween, and having atapered face; wherein the tapered face of the at least one conicalelement engages an inner surface of the ramp elements for forcing theexpanding segments radially outward from the axis; characterized inthat: there are two conical elements, each frustroconical, disposedcoaxially with their bases facing each other; and the inner surfaces ofthe ramp elements are V-shaped.
 2. Tire building drum, according toclaim 1, wherein when the conical elements move farther apart from oneanother, they urge the ramp elements radially outward from the axis. 3.Tire building drum, according to claim 1, further comprising: in eachflange, a first plurality of grooves disposed on an inner surfacethereof and extending radially from the axis, for radially guiding theplurality of ramp elements.
 4. Tire building drum, according to claim 1,further comprising: a plurality of base members supporting a pluralityof fixed segments; in each flange, a second plurality of grooves forreceiving opposite side edges of a the plurality of base members. 5.Tire building drum, according to claim 1, wherein: the conical elementshave notches at circumferential positions about the outer surface oftheir respective bases for receiving a bottom edge of the base member.6. Tire building drum, according to claim 1, wherein: the expandingsegments, ramp elements, flange and conical elements are all located ina center section of the drum.
 7. Tire building drum, according to claim1, wherein: both of the two conical elements exerts a force on each ofthe ramp elements.
 8. Tire building drum, according to claim 7, wherein:the forces exerted by each of the two conical elements are symmetricalabout the centerplane.
 9. Tire building drum, according to claim 1,further comprising: a plurality of fixed segments disposed between theplurality of expanding segments.
 10. Tire building drum, according toclaim 1, wherein: end portions of the expanding segments are contouredto have pockets for receiving components of a tire carcass being laid upon the drum.
 11. Tire building drum, according to claim 1, furthercomprising: biasing members exerting a collapsing radial force on theramp elements.
 12. (canceled)
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